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Wet Spreaders

Diesel-proof patch

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My aluminum fuel tank has sprung a leak - probably just old and corroded. I have the option to replace, but it’s spendy and the vendor is not returning calls. Can I patch with epoxy/glass or will diesel rot the epoxy?

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Mine too, but I'm looking for welder, just have to empty it, unbolt everything, then get it out of the boat - no problem, gulp.

Greg

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Get it welded - using epoxy would be a "get you home" bodge.

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diesel fumes

 

water

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water

or fill it with argon, I suppose...

Still - getting it welded is something I need to organize (and pay for). Slapping some JB Weld over the hole is something I can take care of at the boat in an hour.

I recall a service in the UK that would take your old gas tank from a car that wasn't manufactured any more (think TR6 - etc) with a gas tank rotted out by road salt, and return it to you covered in glass fiber, painted black and ready to install. If I was confident that Diesel won't rot the epoxy, I could easily slap some glass over the bottom and stop it corroding for good and all....

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My aluminum fuel tank has sprung a leak - probably just old and corroded. I have the option to replace, but it’s spendy and the vendor is not returning calls. Can I patch with epoxy/glass or will diesel rot the epoxy?

Throw it away 

check the tank cat for a replacement 

http://moellermarine.com/off-the-shelf/fuel-tanks/permanent-fuel-tanks/

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or fill it with argon, I suppose...

Still - getting it welded is something I need to organize (and pay for). Slapping some JB Weld over the hole is something I can take care of at the boat in an hour.

I recall a service in the UK that would take your old gas tank from a car that wasn't manufactured any more (think TR6 - etc) with a gas tank rotted out by road salt, and return it to you covered in glass fiber, painted black and ready to install. If I was confident that Diesel won't rot the epoxy, I could easily slap some glass over the bottom and stop it corroding for good and all....

Not sure this would even work on a boat because the tank is much smaller, but we used to do it with oil tanks all the time. See if you pull a vacuum on it to stop it from leaking and then slap the JB Weld on. I suppose you could just drain the tank too, but that can be a pain in the ass. If it's still leaking, you'll prob have to rip it out and properly weld it.

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My aluminum fuel tank has sprung a leak - probably just old and corroded. I have the option to replace, but it’s spendy and the vendor is not returning calls. Can I patch with epoxy/glass or will diesel rot the epoxy?

JB makes a fuel tank patch with epoxy and glass pretty cheap. $11 to see if it works seems pretty reasonable. 

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JB makes a fuel tank patch with epoxy and glass pretty cheap. $11 to see if it works seems pretty reasonable. 

Yup, this is the stuff:

https://www.amazon.com/J-B-Weld-8217-TankWeld-Repair/dp/B00R2CDUWE/ref=sr_1_1?s=automotive&ie=UTF8&qid=1521816715&sr=1-1&keywords=fuel+tank+patch

I used it to fix a leaking 55 gallon drum of diesel in the middle of the Serengeti (not hospital clean, to say the least) and it worked as advertised.

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3000 F arc, diesel fumes, what could possibly go wrong!

 

Ummmmm - you clean it out first and preferably remove it from the boat.

No-one will weld a tank that hasn't been thoroughly cleaned.

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Weld it, or replace it.  Did it corrode through from sitting in water, or from the inside out?  

If it's a simple size/shape an off the shelf plastic or new aluminium tank won't be that expensive.  If it's a puncture I'd have it welded and done.  For corrosion though, I wouldn't want to do the same job again in a year or two so replace if it rotted from the inside out.   Whether you fix or replace, put these in: http://www.seabuilt.com/  Now you can open it and clean it properly once in a while and get water out.   Although there's debates about the acceptability of it in some boats I will clear coat the tanks often if it's in a constant wet area.   I recognize the rules about not painting the outside of aluminium tanks because of poultice corrosion, and inability to inspect.  However if it's in an area that gets wet, I would still wash it with aluminum brightener and give it a quick coat of Sharkhide(wipe it on don't spray) or Nyalic (spray it on don't brush) will keep corrosion from happening on the outside for years, and you can see any that starts just as well as a bare tank.    Cheapskate version is just give it a blast of Mercury corrosion guard it's somewhat self healing and lasts well.

 

 

 I did open up a boat that was leaking gas and found someone had patched a tank with a bit of pop can and some JB-weld years before.  It stopped the hole for long enough for the tank to finish rotting out around the patch instead.   Did buy the guy a couple years, but the moment when the patch let go and he was out fishing in some large waves was apparently quite exciting. 

 

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I have heard that some people use CO2 from CO2 fire extinguishers to fill a tank before welding. But empty, wash thoroughly, etc. first.

If I was doing it commercially I'd use CO2 gas from a tank as well; argon costs a lot more!

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I have heard that some people use CO2 from CO2 fire extinguishers to fill a tank before welding. But empty, wash thoroughly, etc. first.

If I was doing it commercially I'd use CO2 gas from a tank as well; argon costs a lot more!

And for all the 150$ish expense, add a seabuilt access plate!  Somewhere I have photos of a 500L tank from an engine that had intermittent stalling problems... It had been cleaned and fuel polished several times in every way possible.  Finally we got it and put in an access plate and found the welding glove from the guy who built it years before.  I brought the glove back to the shop and I believe they gave it back to him.  Interestingly the tank was still nasty inside after all that cleaning, don't see how anyone expects to get them spotless without.  We put in a port on both sides of the baffles, and blasted the piss out of it with a pressure wash with an adjustable head. 

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And for all the 150$ish expense, add a seabuilt access plate!  Somewhere I have photos of a 500L tank from an engine that had intermittent stalling problems... It had been cleaned and fuel polished several times in every way possible.  Finally we got it and put in an access plate and found the welding glove from the guy who built it years before.  I brought the glove back to the shop and I believe they gave it back to him.  Interestingly the tank was still nasty inside after all that cleaning, don't see how anyone expects to get them spotless without.  We put in a port on both sides of the baffles, and blasted the piss out of it with a pressure wash with an adjustable head. 

It has an access plate, although the hole under it is a little small - 1.5" or so - probably too small to get a pressure washer inside and pointed in the right direction, but OK for inspection and access to pump it dry.

I'll pull the tank this weekend and take a look at it. I suspect that the problem is corrosion from the outside because we do get seawater under the tank from time to time - I pump the cavity out manually after racing (does not drain to bilge, obviously) and I run a dehu, but I'd be surprised if the was no damp electrolyte in contact with the tank. It's also under the couch cushions, so someone could have dropped a penny under the tank - that might do it. I'll find out and then decide what to do. Thanks for the advice.

WRT not painting - it's painted right now. Should I strip it? 

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It has an access plate, although the hole under it is a little small - 1.5" or so - probably too small to get a pressure washer inside and pointed in the right direction, but OK for inspection and access to pump it dry.

I'll pull the tank this weekend and take a look at it. I suspect that the problem is corrosion from the outside because we do get seawater under the tank from time to time - I pump the cavity out manually after racing (does not drain to bilge, obviously) and I run a dehu, but I'd be surprised if the was no damp electrolyte in contact with the tank. It's also under the couch cushions, so someone could have dropped a penny under the tank - that might do it. I'll find out and then decide what to do. Thanks for the advice.

WRT not painting - it's painted right now. Should I strip it? 

oh, so you are not sure where the leak is from at this time?    Why doesn't the compartment drain to the bilge(A good design if water is kept OUT of the space of course, but many tanks are right in the bilge, so drainage may be sensible if water gets in regularly)?   I would do a little more investigating first before getting too involved with the tank.  Have you checked the basics out already(fittings, sender, hoses)?  Fuel sender gaskets are chronic sources of leaks.  Does it drain all of it's fuel out or only leak a little?  If you consistently lose fuel to the same level that can indicate where the leak is if on the tank.  If it drains consistently and you're just finding fuel, it could be a lower point in a hose siphoning, do the hoses dip down below the tank level in that compartment?   A good first step is to clean around the tank, and clean the tank well, then put absorball mats(the white kind that only absorb petroleum products) around the edges and underneath.  Pressure the tank up a bit(just a few PSI), wet the fittings with leak detector(dish soap and water is a mediocre but better than nothing version) and start checking the mats to see where the leak is and how much is coming out if the fittings don't bubble.  Single location small quantity could even be something as simple as a pinhole in a weld rather than a serious corrosion problem.   Multiple locations at once, I'd err on the side of replacement rather than reuse, if it'll be wet all the time I'd switch to plastic if one will fit.

Do you have a photo of the tank/location?

Not painting applies to new tanks only as far as I know(it's a pet peeve of our local surveyor, painted tanks are second only to the foaming in of tanks for that), not required to strip, though if you find the leak is from corrosion I would definitely strip to check for other problems.     A coating like sharkhide works wonders for tank longevity in wet locations(dry is better of course) and the surveyor doesn't complain so it's my usual go to for aluminum tanks in wet locations.  

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Here's the tank - out of the boat, cleaned and wire-brushed. I sharpied the suspicious areas of corrosion. I'm pretty sure that it has more than one hole in the aluminium and that the diesel was only being kept in the tank by the 1/2cm of biofilm that I hosed out of it.

 

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The corrosion on the tank was aligned with the rubber bumper strip on the floor supporting it. Obviously it had trapped salt and that's what made it etch away.  When I put it (or a new one) back in, is there a kind of honeycomb type material that I can use as a bumper instead of flat stickyback foam? Something that suspends the tank, spreads the pressure, but dries out easily?

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Phew, that's swiss cheese...I'd say it's gonzo. Why not just make it's replacement a tad smaller so it is suspended and not touching anything? Mine's coming out tomorrow, but it is fully suspended and has air flow around the whole tank. I suspect one of the L's welded onto it is where my leak is....we'll soon see.

Greg

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I had a tank just like that - well, not that bad. Basically the low corner of the tank sat in an area that didn't dry and it eventually corroded from the outside. I pulled it out of the boat (how easy that sounds...) cut the corner of corrosion off and had a plate welded on making the tank a little smaller. That low corner doesn't actually enclose much volume, so the difference was quite small. The rest of the tank was as good as new. 

When I put it back in, I set it on Dri-Dek. It supports the tank well enough but allows a lot of ventilation and you can even hose underneath it if the area is limbered. Contact to the tank is limited to a bunch of little dots, not a huge area that stays wet forever. 

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From the pic it looks like a patch would do the trick - is that area the only bad part? If so, cutting that strip off and welding in new would seem to be the quickest, easiest and cheapest way to go.

How about setting it on a bit of that plastic grid that is used for diffusers on big fluorescent light fixtures? Really cheap but stiff.

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1 hour ago, SloopJonB said:

 

How about setting it on a bit of that plastic grid that is used for diffusers on big fluorescent light fixtures? Really cheap but stiff.

I have some polypro chickenwire (solid plastic - no metal). I'm thinking that a couple of layers of that would be better than foam - somewhat conforming, but would allow air to circulate and water to drain away.

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In powerboats, we replace tanks pretty regularly that sit in a bilge area.  We don't usually fix them.  Plastic tanks tend to crack, although they're very common in new boats.  If you're keeping the boat, buy a new tank- make sure the builder can certify it.

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On 3/26/2018 at 11:17 AM, Wet Spreaders said:

I have some polypro chickenwire (solid plastic - no metal). I'm thinking that a couple of layers of that would be better than foam - somewhat conforming, but would allow air to circulate and water to drain away.

To me that much corrosion says replace.  I'd be surprised if you save more than 200-300$ by fixing if that is a reasonably simple shaped tank which it looks to be.  But if re&re is free, and access is easy, and you can get a welder with previous certified fuel tank construction experience who will cut and weld it, and sign off on the job with a pressure test, I would maybe consider it if the tank is some super oddball shape you absolutely can't replace with something off the shelf for about the same as a welder who is good enough to trust to do the job properly will charge.  Foam sucks.   I suppose the chicken mesh might work, but why not use something that's at least quasi designed for the job?  Think draining tiles as used on pool decks.  Easy, cheap snap together.  I'd still Nyalic or corrosion guard the areas that sit on there at least(nyalic better, you can even buy it in a spray bomb) Sure it will eventually wear off, but it'll buy you time.  Which is all you can really expect with an aluminium tank that gets wet especially one in that condition.   If it buys you a few years to the start of corrosion and that buys you another 5 years before failure, is that enough?

Have you inspected the inside for corrosion?  If any is there, and you see those problems on the outside I would again err on the side of replacement. 

If you were in my shop with a tank like that and this was a "we absolutely can't afford any other solution" and you signed off that I was not responsible for the tank lasting and only for the labour on the re&re, I would maybe consider it, but still be unhappy about it.  I couldn't take your money and feel good about it for sticking that back in.  Can you post the dimensions of the tank?  You've already got labour and abrasives spent, but that's a sunk cost at this point.  I want to see if I can find you a part number for a close fitting replacement so you at least have a reference when you're getting prices for the repairs.  

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12 hours ago, jgbrown said:

To me that much corrosion says replace.  I'd be surprised if you save more than 200-300$ by fixing if that is a reasonably simple shaped tank which it looks to be.  But if re&re is free, and access is easy, and you can get a welder with previous certified fuel tank construction experience who will cut and weld it, and sign off on the job with a pressure test, I would maybe consider it if the tank is some super oddball shape you absolutely can't replace with something off the shelf for about the same as a welder who is good enough to trust to do the job properly will charge.  Foam sucks.   I suppose the chicken mesh might work, but why not use something that's at least quasi designed for the job?  Think draining tiles as used on pool decks.  Easy, cheap snap together.  I'd still Nyalic or corrosion guard the areas that sit on there at least(nyalic better, you can even buy it in a spray bomb) Sure it will eventually wear off, but it'll buy you time.  Which is all you can really expect with an aluminium tank that gets wet especially one in that condition.   If it buys you a few years to the start of corrosion and that buys you another 5 years before failure, is that enough?

Have you inspected the inside for corrosion?  If any is there, and you see those problems on the outside I would again err on the side of replacement. 

If you were in my shop with a tank like that and this was a "we absolutely can't afford any other solution" and you signed off that I was not responsible for the tank lasting and only for the labour on the re&re, I would maybe consider it, but still be unhappy about it.  I couldn't take your money and feel good about it for sticking that back in.  Can you post the dimensions of the tank?  You've already got labour and abrasives spent, but that's a sunk cost at this point.  I want to see if I can find you a part number for a close fitting replacement so you at least have a reference when you're getting prices for the repairs.  

Thank-you for your concern and offer of help. I finally managed to contact the original manufacturer - they don't answer emails, but are very friendly on the phone - and bought a new tank ($500 inc shipping). However, it's not going to be ready before our next regatta and so I have fixed the old one using MarineTex Grey - which is alleged to be diesel-proof - with a coat of glass and some more epoxy over the top. All items that I had in my garage left over from building an El Toro. I have not done a pressure test yet - I need to come up with a way to seal off all of the access ports and connect a compressor and a pressure gauge. I'm thinking something like 5 psi as the test pressure - should I go higher? The alternative would be a vacuum test, which might be easier to seal tight, but is less representative of the pressure (in to out, rather than out to in) that I'm trying to withstand.

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Be very careful on pressure testing a flat walled tank. I'm not sure what the standard is, but if you have say 3 sq ft in the side of that tank, 5 psi is over a ton of pressure on the plate. 

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1 hour ago, DDW said:

Be very careful on pressure testing a flat walled tank. I'm not sure what the standard is, but if you have say 3 sq ft in the side of that tank, 5 psi is over a ton of pressure on the plate. 

Good point. 

My idea was to block the inputs/outputs, fill with water and then hit it with the compressor - check for leaks. A gentler way to do it would be to fill with water and simply raise the fill tube a few feet higher than the tank. My recollection is that 10ft of water is an atmosphere (15 psi) and so I only need 3 ft of hose to apply the pressure and it's less likely to create a monster bang if my calibration is off on my compressor gauge.

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One more point - the inspection port has a rubber gasket and a bunch of stainless bolts tapped directly into the 0.090" thick aluminum sheet metal. Do I torque this down dry or should I put some kind of gasket sealer on it?

 

 

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33 ft of water is one atmosphere, or 14.7 psi. But your idea of a water column instead of a compressor is a good one. You want very careful limits on the pressure, not easy with a compressor and a 100 psi gage that is probably +/- 10 psi.

Another possibility is to put some water in with a little alcohol. That lowers the viscosity and will show smaller leaks. 

I'd put some kind of diesel proof sealer on it - the problem with .090 aluminum is its pretty hard to get much pressure on the gasket, the aluminum just bends unless there is a doubler. 

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For sealant I use Mercury Perfect Seal.  Doesn't dry out much.  Thiss also what my preferred(and certified) tank builder uses.  Put it on the screw threads too for sealing and anti seize function.

I prefer air testing, use soapy water to check for leaks.  A ghetto rig version if your compressor isn't finely adjustable is to buy a skinny road bike inner tube for a tire size the same as your pick-up fitting and cut out a section. It'll stretch over the vent fitting as well with a little effort, then double clamp it(usually 3/8 pick up 5/8 vent here).  Pump it up by hand using a bike pump with gauge.  Disconnect and check for leaks.  Then leave it for a few hours.  If pressure drops while temps are the same(indoors). Look harder for leaks.  

 

Very glad you plan to replace. Mmuch better long term. 

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